FDA Category 2 Peptides and Semaglutide Safety Signals

Clinical Question

What is the current regulatory status of commonly compounded peptides, and what safety signals have been identified in recent clinical data and post-marketing surveillance?

Evidence Snapshot

• Regulatory Alignment: Multiple peptides classified as Category 2 bulk substances (ineligible for routine compounding).
• Compounding Status (503A/503B): BPC-157, TB-500, and GHK-Cu remained in Category 2 as of September 2023.
• Safety Signals: Emerging FAERS signals for Semaglutide include NAION (96 cases through Dec 2024), pulmonary aspiration (added to label 2025), and intestinal obstruction.
• Clinical Outcomes: Phase III weight loss results range from 14.9% (Semaglutide) to 22.5% (Tirzepatide).

What the Research Shows

Regulatory and Compounding Status As of March 2026, the FDA has designated several peptides as Category 2 substances under Section 503A or 503B, citing significant safety risks or lack of safety data. BPC-157 is classified as a Category 2 bulk substance due to immunogenicity concerns and a lack of safety data, making it ineligible for routine compounding. Similarly, TB-500 (Thymosin Beta-4) is listed in Category 2, with the FDA citing immunogenicity risk and a total lack of human exposure data.

GHK-Cu is also categorized as a Category 2 substance for both 503A and 503B due to immunogenicity risk, and it is not an FDA-approved injectable drug. Several substances previously nominated have seen their status change; for instance, the nominations for AOD-9604, Ipamorelin, Selank, and CJC-1295 were withdrawn in September 2024. CJC-1295 was specifically noted by the FDA for safety issues including increased heart rate.

Thymosin Alpha-1, though approved in over 35 countries as Zadaxin, is not FDA-approved. It was moved to Category 2 in September 2023, then removed pending advisory review in September 2024, yet it remains a substance of concern under interim policy.

Post-Marketing Safety Signals Post-marketing surveillance of GLP-1 receptor agonists has identified several safety signals. Semaglutide, which has over 187,757 associated adverse event reports through 2023, shows strong signals for gastrointestinal issues including nausea, vomiting, and delayed gastric emptying.

Emerging signals for Semaglutide include Nonarteritic Anterior Ischemic Optic Neuropathy (NAION), with 96 cases reported through December 2024; this is currently under EMA review as of January 2025. Furthermore, pulmonary aspiration was added to the Ozempic label in 2025, noted as a risk during general anesthesia due to delayed gastric emptying. Other signals involve acute pancreatitis (moderate signal), acute kidney injury often related to GI-related dehydration, and cholecystitis associated with rapid weight loss.

Clinical Trial Outcomes Clinical evidence for approved peptides demonstrates significant efficacy in specific indications. In the STEP 1 trial (NCT03548935), Semaglutide achieved 14.9% weight loss in obesity. Tirzepatide demonstrated 22.5% weight loss in the SURMOUNT-1 trial (NCT04184622) and showed superiority over semaglutide in the SURMOUNT-5 trial.

Conversely, some clinical data has been negative. A Phase III trial (NCT02867267) for Thymosin Alpha-1 in sepsis showed no mortality reduction. Tesamorelin has demonstrated efficacy in HIV lipodystrophy with an 18% reduction in visceral adipose tissue (VAT) (NCT00451282).

Mechanism

Mechanistic data is limited in the provided records. The data notes that BPC-157, TB-500, GHK-Cu, and GHRP-2 are associated with immunogenicity risks. For CJC-1295, the FDA cited heart rate increases as a notable safety issue. For Semaglutide, delayed gastric emptying is identified as a contributing factor to pulmonary aspiration and may impact the absorption of oral medications.

Limitations of the Evidence

There are significant gaps in the human clinical data for several peptides. Specifically, the FDA notes a total lack of human exposure data for TB-500. For BPC-157, the primary limiting factor is a lack of general safety data.

Regarding post-marketing signals for Semaglutide, suicidal ideation is currently under evaluation, though the FDA notes current data do not support a higher risk compared to background rates. Additionally, while Selank and Semax are approved for use in Russia, they lack FDA approval or extensive clinical trial data within the U.S. regulatory framework.

Clinical Takeaway

Regulatory authorities have curtailed the availability of several peptides, including BPC-157 and TB-500, by placing them in Category 2 due to immunogenicity concerns and insufficient human safety data. While peptides like Semaglutide and Tirzepatide demonstrate significant weight loss efficacy, ongoing surveillance has identified emerging risks such as NAION and pulmonary aspiration. Physicians should note that many commonly discussed peptides currently lack FDA approval and may be subject to warning letters or compounding restrictions.

Sources

1. FDA Regulatory Status Record ID: 0abdad3c-4489-493d-9407-b7016c5cb62b (BPC-157)
2. FDA Regulatory Status Record ID: 68b0b103-e422-42e2-803f-b9f91c6ecc5e (Thymosin Alpha-1)
3. FDA Regulatory Status Record ID: c8181049-d986-4a2f-8b55-2bf1e9eacaea (TB-500)
4. FDA Regulatory Status Record ID: 1a160b34-1002-4213-9a8a-95697b6004d8 (CJC-1295)
5. FAERS Safety Signal Record ID: be753983-70d7-47cd-a7a2-359030bae94f (Semaglutide/NAION)
6. FAERS Safety Signal Record ID: 60c7beaa-31a4-4a0e-974c-9728347759ca (Semaglutide/Pulmonary Aspiration)
7. Clinical Trial Record ID: 65446b68-60de-4313-bc2f-f39e15eef52e (STEP 1)
8. Clinical Trial Record ID: 91163f2f-7b8b-47dd-b57e-f332dee1d87a (SURMOUNT-1)

This content is sourced exclusively from TruthTides clinical reference data and does not constitute medical advice.